This is a perfect bar cookie. It's a buttery, butterscotchy, rich and gooey, nutty-crunchy, and then oh my god there's salt on top sort of treat.
Preheat the oven to 350 degrees. Grease an 8- or 9-inch square baking pan.
Combine the cookies and melted butter in a food processor or blender with a pulse mode. Press it into the pan. Bake for about 10 minutes, or until lightly golden on the edges. Remove from the oven.
Meanwhile, in a small saucepan, combine the butterscotch chips, corn syrup, butter, cream, and vanilla. Cook and stir over medium heat until smooth.
Spread over crust. Sprinkle with the nuts; press down lightly. Bake for 11-13 minutes or until topping is bubbly and lightly browned. Cool on a wire rack. Sprinkle with coarse sea salt. Cut into bars.